Thanks OCE_Arne, as suspected there was a line fault. It was fixed on Sunday evening.
What is the situation as regards lack of service - is the monthly charge reduced pro-rata?
I did have a call from someone in the technical department after the fault was repaired and I mentioned to him the difficulty there is in reporting a simple line fault. I actually spent from 11:30 to 21:30 on the Friday trying to report the fault and get acknowledgement. I also needed to switch on the call divert (which I pay for), but there is no mechanism to do this, except by using the phone, which was down.
It would be really helpful if there was a section on the TalkTalk website where fault details could be entered (and call divert offered) with an e-mail confirmation then being send. Once, it was only necessary to call BT with the faulty telephone number and action was then taken.
Thank you for helping to fix this problem.